1. Field of the Invention
The present invention relates to support structures, such as decking produced from plastic lumber materials, or pallets, for instance pallets on which articles are stacked or assembled to enable handling and shipment of articles. More specifically, the present invention relates to support structures that can be easily assembled in modular fashion in several configurations to provide continuous top and bottom surfaces, and at a minimal expense, and that can be easily assembled, disassembled and reassembled as needed for maintenance.
2. Description of Related Art
Historically, pallets have been constructed with wood materials, having a plurality of parallel stringers on which are nailed or otherwise secured one or more structural members defining a platform. Pallets and decking have also been constructed of extruded or formed metal such as steel or aluminum, and also been molded or extruded plastic materials, including virgin plastic material or plastic material that has been recycled or reclaimed from waste. The materials used in said pallets and said decking are typically connected using mechanical fasteners or bonding agents.
Support structures of this type that are constructed of plastic have unique problems. For decking applications, the existing solid plastic lumber is heavier than the conventional wood deck and requires nails, fasteners, or adhesives to hold it together. Most pallet designs do not have interlocking sections and as such require fasteners.
Current designs for pallets utilizes fasteners to build structure into the pallet. The U.S. Air Force uses a balsa-wood pallet with aluminum skin to transport cargo in the cargo planes. The aluminum skin is attached to the balsa wood core material with adhesives and rivets. This design causes the pallet to be heavy and also requires the pallet to be repaired at the manufacturing facility in Minnesota. There is a need, then, for a pallet that is lighter, less expensive, and easier to repair than the current balsa wood pallet.
For wood decking applications, the wood and most plastic lumber materials are solid and are attached with nails into cross beams. Bending stresses in such a decking application occur on the top and bottom surfaces, but the solid material is used is very heavy.
Prior patents in the area of pallets and decking offer sections that do not interlock simply, but rather require fasteners or other connecting structures or devices. In such prior designs it is difficult to create and maintain a continuous surface across the top or bottom of the structure, as the structural elements used in such pallets or decking are connected with mechanical fasteners or bonding agents.
Prior art structures include U.S. Pat. No. 5,921,189, to Estepp, for a pallet made from a rectangular tubular elements of open ended plastic material in adjacent parallel contact, which and are fastened at outer sidewalls and at the ends by a fastening device.
U.S. Pat. No. 5,809,902, to Zetterberg, describes a pallet comprised of a solid deck comprised of rail elements that are attached together with at least two elongated, angularly folded fixing members that attach with insertable grooves made in the boards transverse to their longitudinal direction. The fixing member is made of metal as an angle piece with flanges. The grooves and fixing member engage on top surface and on perpendicular side face. The grooves are cut into deck material perpendicular to longitudinal direction
In Zetterberg the fasteners are required to secure the separate sections. The separate sections are connected with a modified angle iron that engages only at the ends of the rail elements. The middle sections of adjacent rails are not connected or secured to one another for support.
In some prior devices the side walls and not the top and bottom walls have an interlocking structure. A side-wall connecting pallet requires fasteners and/or adhesives to hold the structure together. The side-connecting plane results in a shearing plane being formed when weight is added to the top surface. The weight in loaded on the top surface, which is perpendicular to the side-interlocking surface. This is the cause of the shearing plane. The shearing plane is on the side walls and will result in the side walls separating as the weight on the top surface causes the pallet to bend. Thus the side walls still must be attached via mechanical fasteners and/or bonding agents. Current designs for pallets and decks utilize adhesives or fasteners to build structure.
No pallet or decking of the prior art provides sections that interlock and form a continuous surface on top or bottom. Thus there remains a need for a modular support structure that does not require special fasteners or bonding agents.